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Old 27th May 2008, 01:41 PM   #1
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Default Super Audiophile Phono-Stage - Battery Powered

After a disgusted failure with my attempted construction of a high quality phono stage from scratch I turned my attention, to much horror of the thing, to my Pro-Ject Phonobox II.

The Phonobox II is powered by 16v AC from a wall-wart tranny. Some audiophiles are appalled by this configuration so I thought I should for once address the "problem".

Opened up the unit and scanned around the PCB... found the two little chips (full of smoke). 79L15 & 78L15 IC regulators, which attempts to filter and smooth the half-wave AC from the single feed AC supply.

I carefully removed the two (yes only two!) diodes that divides the single phase AC current into two out-of-phase half-wave feeds. Also removed the AC input jack.

A nice cable was prepared and carefully soldered in place to feed the two regulators with < [+] [GRND] [-] > from the two 12v (-12v 0v +12v) batteries.

Wow! Am I surprised by the increase in sound quality! Look, the Phonobox II is actually a bloomin good RIAA pre-amp compared to pre-amps costing tenfold. (These days every pre-amp designer uses Op-Amps anyway... there is only a few left that has the guts to design a pre-amp using discreet components).

The sound-stage projected by the speakers suddenly has air and is almost tangible. My blasted hum is virtually gone and overall sound is inviting!

I am very pleased I took the plunge at converting the Phonobox. I wanted to do so for a long time but was scared. The tinkering with pre-amp building taught me one thing for sure - how a regulator looks and works! So there you go!

D
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Old 27th May 2008, 03:32 PM   #2
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Nice! Have you considered building your own diy power supply for it, or will you just leave it running off of the batteries?

-Justin
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Old 27th May 2008, 03:43 PM   #3
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Quote:
Originally posted by despotic931
Nice! Have you considered building your own diy power supply for it, or will you just leave it running off of the batteries?

-Justin
Justin

Luckily I have a lot of these "alarm" 12v batteries and will continue to use them. That was the idea from the start.

I will look into building a simple mains PSU for the phonostage but for now I am happy!

Sound is alive and airy! I love it!

D
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Old 27th May 2008, 03:56 PM   #4
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Quote:
Originally posted by despotic931
Nice! Have you considered building your own diy power supply for it, or will you just leave it running off of the batteries?

-Justin


Why?

The only reason that miserable thing sounds good are the batteries. Nearly impossible to get any PS/regulator to sound the same.

The "battery" sound is very impressive in immediacy, air and detal. There are some shortcomings though.
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Old 27th May 2008, 04:18 PM   #5
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Quote:
Originally posted by analog_sa

The "battery" sound is very impressive in immediacy, air and detal. There are some shortcomings though.
Hello Analog SA! Have we met before?

Yes... like I said before - the sound is airy and focussed!

What shortcomings are there?

D
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Old 27th May 2008, 09:48 PM   #6
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Originally posted by GlidingDutchman


What shortcomings are there?

For one, you have to replace them. ie. buy new.

For two, you have to recycle them. ie. pay someone to take the old away.

If you don't do two, then please start.
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Old 27th May 2008, 10:03 PM   #7
tubenut is offline tubenut  South Africa
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Battery drawback?

Other then "green issues", dynamics for one imo/experience.
Different batteries also sound different btw...

In comparison to what reference are you calling this thing a "Super Audiophile Phono-Stage "?

It is not bad for the money in comparison to commercial options, better once some modifications are done to poor quality filter components and quite listenable but audiopile? Depends on what that means to the individual I guess.


Compares well to tenfold the price? What have you tried? For one the Clearaudio Smartphono craps all over it for say 3* the price. At ten times the price it is another ballgame all together and it is left far behind.
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Old 27th May 2008, 11:48 PM   #8
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Quote:
Originally posted by GlidingDutchman


Justin

Luckily I have a lot of these "alarm" 12v batteries and will continue to use them. That was the idea from the start.

I will look into building a simple mains PSU for the phonostage but for now I am happy!

Sound is alive and airy! I love it!

D
Ahh, the reason I ask is that I was considering purchasing a phonobox and then building a new power supply for it, But didn't want to take the battery powered route.

Quote:
Originally posted by analog_sa




Why?

The only reason that miserable thing sounds good are the batteries. Nearly impossible to get any PS/regulator to sound the same.

The "battery" sound is very impressive in immediacy, air and detal. There are some shortcomings though.
Batteries are a continual cost, something that will be a continual drain of my funds. These are funds that are short already, and I know these batteries are quite costly. I don't doubt that it doesn't sound way better than the stock psu, but I also believe that you could build a custom psu that would be much better as well.

-Justin
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Old 28th May 2008, 07:38 AM   #9
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Quote:
Originally posted by tubenut
Battery drawback?

Other then "green issues", dynamics for one imo/experience.
Different batteries also sound different btw...

In comparison to what reference are you calling this thing a "Super Audiophile Phono-Stage "?
Dynamics are now better than ever as opposed to the crude AC system...

The thread name? Just to draw attention -

Yes, I am aware that there are designs that will whack it in the face but for now it sounds marvellous!

D
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Old 28th May 2008, 07:43 AM   #10
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Originally posted by shallbehealed


For one, you have to replace them. ie. buy new.

For two, you have to recycle them. ie. pay someone to take the old away.

If you don't do two, then please start.
Replace them how often? Every few years? Not a big deal I think...

Recycle - whats that? I live in Africa!

(Dont worry... I wont dump the used batteries on the wasteland. We have a scrap metal recycle yard here in town that recycles lead products)

D
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